Soft capsules generally consist of a gelatin shell which is produced by extending a mixture of gelatin, plasticizer, and water into a thin sheet. Gelatin, which is normally utilized in such formulations, is defined as a protein obtained by partial hydrolysis of mammalian collagenous tissues, such as skins, tendons, ligaments and bones. Gelatin may also be derived from fish. Capsules formed from such a gelatin sheet may hold a wide variety of substances. The shell of a soft capsule is typically produced by adding, to a gelatin, a plasticizer in an amount of 30-40 wt % with respect to the gelatin, and drying the shell until the water content becomes 5-10%. Depending on the formulation used, once a soft capsule is placed in the mouth, the gelatin allows rapid dispersion of the dosage form.
“Chewable soft” capsules are a type of soft gelatin capsule that is particularly distinguished by both a pleasant chewing experience and a complete or near complete dissolution in a short period of time in the oral cavity. Such capsules are also distinguished by particular fabrication problems, such as excessive stickiness during rotary die encapsulation and sticking of the product to other capsules during post-encapsulation handling. Gelatin capsules with high end water content typically have poor storage performance, sticking to one another in bulk packaging to form an agglomerated mass and often melting during storage. In order to prepare the capsules for packaging and storage, the capsules are generally dried in one or more dryers where the capsules are tumbled while exposed to heated gases at a controlled humidity level.
Following the encapsulation process and the tumble dry process, the capsules may be transferred to numerous subsequent steps in final preparation for packaging. One additional process used to combat capsule stickiness is to transfer the capsules into a polishing pan whereby the capsules are coated with a dusting agent. Most often, the dusting agent is a starch, typically potato or corn starch, although tapioca starch, wheat powder, waxy corn starch powder, and partial alpha starch powder, as well as others, are also effective. The capsules may then be tumbled to produce an even coating of starch. The starch coating inhibits the capsules from sticking to one another. To separate the excess starch from the coated capsules, the capsules are transferred onto a vibratory sieve where they are vibrated to remove excess coating material.
Besides the obvious disadvantages of having additional steps and equipment in a manufacturing process, there are other difficulties associated with the coating process. One such problem is excessive particulate air pollution caused by starch particles becoming airborne. Not only are the airborne particulates a respiratory hazard, but they are an explosive hazard as well. Other problems include respiratory problems, induced by dust, of the machine attendants required to operate the equipment, and, to a lesser extent, housekeeping issues associated with having any type of uncontained powder in a manufacturing environment.
What has been needed is a system of dusting capsules with containment of the dusting agent to reduce exposure of personnel and vital equipment to the dusting agent and to reduce the explosive potential created by airborne dusting agent. The art also has needed a system that does not require sieving and that provides a consistent, controllable coating with efficient use of the dusting agent.